Rapid thermal processing (RTP) subjects a substrate to brief intense bursts of heat. RTP technology can be used to change the characteristics of a deposited film or crystal lattice and generally includes processing such as annealing, silicidation, and oxidation of a substrate surface.
Generally, an RTP chamber includes a radiant heat source, a chamber body, a substrate support, and a process gas supply system. The radiant heat source is typically mounted on a top surface of the chamber body so that the energy generated by the heat source radiates upon the substrate supported by the substrate support within the chamber body. Processing gases are usually supplied to the chamber from one or more gas inlets. When two process gases are used, for example hydrogen (H2) and oxygen (O2), they are typically introduced to the chamber from separate gas inlets or they may be premixed before being delivered to the process chamber through a single inlet.
The inventors have observed that process gases provided from separate gas inlets often provides suboptimal gas mixing which adversely affects process uniformity. For example, the mixing point of the gases may be on the substrate, forming a non-uniform gas composition across the substrate. Furthermore, even where the substrate is rotated, the rotational speed and direction of the substrate adversely affects the uniformity of the mixed gases, further contributing to process non-uniformities.
On the other hand, the inventors have also observed that premixing process gases prior to delivery to the chamber is problematic due to back flaming or flashback which can cause damage to components of the gas supply system. Flashback is a condition in which the flame velocity is opposite in direction and greater in magnitude than the process gas velocity and may extend to the mixing point of the gases. The velocity of premixed process gases is often not great enough to maintain stable combustion of the gas in the chamber.
Accordingly, the inventors have provided improved apparatus and methods for the mixing and delivery of process gases.